Lepidoptera is an order of insects which includes moths and butterflies. It is estimated that there are over 174,000 Lepidopteran species, included in an estimated 126 families. Lepidopteran species undergo a complete metamorphosis during their life cycle. Adults mate and lay eggs. The larvae that emerge from the eggs have a cylindrical body and chewing mouth parts. Larvae undergo several growth stages called instars until they reach their terminal instar and then pupate. Lepidoptera then emerge as adult butterflies or moths.
While some Lepidoptera species are generally considered beneficial organisms due to their aesthetic appeal, many species cause devastating damage to crops. Specifically, diamondback moths, beet armyworms, sugarcane borers, soybean loopers, corn earworm, cabbage looper and southwestern corn borer are especially problematic to crop growers.
Diamondback moths (Plutella xylostella) are a widespread pest that can disperse long distances. Diamondback moth larvae eat the leaves, buds, flowers and seed-buds of cruciferous plants. A heavy infestation can completely remove all foliar tissue from a plant leaving only the leaf veins. Even a lighter infestation can result in the unsuitability of an entire lot of produce for sale. In the past, diamondback moths have been treated with a variety of insecticides including pyrethroids.
Beet armyworms (Spodoptera exigua) are another widespread pest that is difficult to control. The larvae are voracious eaters that defoliate host plants. Older instars can also burrow into the plants. The damage to the host plant renders it unmarketable. Beet armyworms are pests on numerous types of crops.
Sugarcane borers (Diatraea saccharalis) mostly attack sugarcane and sweet corn crops, but will also infest other host plants. The larvae burrow into the stalks of the older plants causing the plant to weaken and break off or die. In younger plants, the inner whorl of leaves will die and yields will be impacted. Secondary fungal infections may also commonly occur as a result of seed cane predation. There has been some success in controlling sugarcane borers with insecticides but they need to be applied to the plants before the larvae burrow into the stalks.
Soybean loopers (Chrysodeixis includens) are a moth that is prevalent in North and South America. The larvae of soybean loopers can inflict heavy foliage damage resulting in significant crop loss. Soybean loopers are difficult to control with insecticides. Infestation of soybean loopers can be exacerbated after a non-selective insecticide removes the soybean loopers' natural predators.
Corn earworms (Helicoverpa zea) have been referred to as the most costly crop pest in the United States. Corn earworms are difficult to control with insecticides because they can burrow into the plants and avoid exposure to insecticide applications. Corn earworms have numerous natural predators but predators and parasitoids alone are not effective at preventing crop plant damage by Helicoverpa zea. 
Cabbage loopers (Trichoplusia ni) are a destructive crop pest in North America. During their larval stage, they eat three-times their body weight in plant material a day. Once they are established in a crop field, they are difficult to control.
Southwestern corn borers (Diatraea grandiosella) cause crop damage in the United States and Mexico. It is estimated that southwestern corn borers cause millions of dollars of damage each year. The first larvae that emerge after overwintering feed on the whorl of the plant and can cause total destruction of the plant (dead heart). The second generation that emerges later in the growing season feeds on leaf axils and eventually bores into the stalks which can cause girdling and can also lead to death of the plant.
Bacillus thuringiensis is a natural soil bacterium. Many Bacillus thuringiensis strains produce crystal proteins during sporulation called δ-endotoxins which can be used as biological insecticides. Bacillus thuringiensis, subspecies aizawai and kurstaki, produce crystals which paralyze the digestive system of some larvae within minutes. The larvae eventually die off from the multiple deleterious effects from toxin interactions with the gut tissues of the target pest. Bacillus thuringiensis subsp. aizawai is commercially available as XenTari® (available from Valent BioSciences Corporation, XenTari is a registered trademark of Valent BioSciences Corporation). Bacillus thuringiensis subsp. kurstaki is commercially available as Dipel® (available from Valent BioSciences Corporation, Dipel is a registered trademark of Valent BioSciences Corporation). Sympatico™ is a commerical product that is a combination of Bacillus thuringiensis subsp. aizawai and Bacillus thuringiensis subsp. kurstaki fermentation solids, spores, and toxins (also available from Valent BioSciences Corporation).
One advantage of using Bacillus thuringiensis subsp. aizawai and Bacillus thuringiensis subsp. kurstaki is that they are target specific. They do not harm humans or other non-target species. Frequently when plants are treated with a non-selective insecticide, the insecticide also kills natural predators of other pests. This can cause a rebound effect in the target insect or other opportunistic pest species. For example, after applying a non-selective pesticide to kill corn borers, a spider mite infestation might occur because the non-selective pesticide also killed the spider mites' natural predators.
Yet another advantage of Bacillus thuringiensis subsp. aizawai and Bacillus thuringiensis subsp. kurstaki is that they can be used on organic crops. With no mandated pre-harvest interval, it can also be used on crops right before harvest. This provides organic growers, who have few options for pest control, a safe and effective way to manage insect infestations that could ultimately ruin an entire crop.
Accordingly, there is a need for safe and effective ways to control diamondback moth, beet armyworm, sugarcane borer, soybean looper, corn earworm, cabbage looper and southwestern corn borer. These methods should be easy to apply, have increased efficacy, and be cost effective.